1. Field of the Invention
The preset invention relates to a method and apparatus in which a device terminal accesses a coordinator terminal in a communication system. More particularly, the present invention relates to a system and method supporting efficient operations of a plurality of sensor devices that periodically transmit sensing information in a Body Area Network (BAN).
2. Description of the Related Art
Wireless Body Area Network (WBAN), which is under standardization as an international standard called Institute of Electrical and Electronic Engineers (IEEE) 802.15.6 TG6 BAN, aims to provide medical services such as telemedicine services over a communication network formed around three meters or less from the body, and to provide entertainment services in which wearable equipment for wearable computing or motion sensors are used. In addition, WBAN is under similar standardization as an international standard called IEEE 802.15.4j Medical BAN (MBAN), and 802.15.4j is defined as an amendment standard for using the existing 802.15.4 in a Medical BAN Service (MBANS) band of 2.36˜2.4 GHz.
WBAN generally includes a coordinator and a plurality of devices such as various types of sensors attachable to the body.
The main application of WBAN is to collect biometric information from medical sensors and to send the collected biometric information to medical institutions. A coordinator, which has a wire or wireless communication line connected to a medical institution server, sends data received from devices or sensors connected by WBAN to the medical institution server. For example, the coordinator may send the data received from the devices or sensors in an unprocessed form or after analyzing such data.
In the WBAN healthcare system, because small-sized devices equipped with a mobile power supply such as a battery are mainly handled, reducing (e.g., minimizing) the power consumption of the devices is an important system requirement. Generally, a low duty cycling technique may be applied, for low-power implementation. As an example, the small-sized devices may be sensors having poor power conditions.
FIG. 1 shows a data transmission process when it is operated by low duty cycling and when a beacon is used in an IEEE 802.15.4 WBAN according to the related art.
Referring to FIG. 1, when the data transmission process is operated by low duty cycling, the lower the duty cycling, the greater the number of nodes that have data during an inactive period. At the starting point of the next active period, the system attempts to transmit all of the data.
As described above, in the WBAN according to the related art, when data is transmitted by low duty cycling, many nodes may have data during an inactive period due to the low duty cycling. Consequently, transmission of all of this data is attempted in the next active period.
In this case, the WBAN according to the related art may deal with contention with the fixed initial backoff settings, for packet transmission. However, when the concentration of traffic is severe, it is difficult to solve this problem with the initial backoff settings which were made without recognizing this problem.
In addition, when a number of packet transmission attempts rapidly increases in the next active period, the packet transmission attempts are concentrated at the same time in a Contention Access Period (CAP). Accordingly, traffic may occur during the packet transmission.
Therefore, a need exists for an apparatus and method for controlling resource access by devices such that in a WBAN in which periodic data transmission is made, a plurality of devices may be prevented from causing a reduction in performance such as delays due to their excessive collisions in a Contention Access Period CAP
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.